1. Field of the Invention
This invention relates to an induction heating cooking unit and more particularly to an assembly of the ceramic cooking surface, the heating units, and the trim, with an underlying support plate for the ceramic sheet that also fixes the position of the heating units held therein by a support bar.
2. Description of the Prior Art
Induction heating units are uniquely adaptable to a smooth-top ceramic cooking surface in that they can be positioned sub-adjacent such cooking surfaces with the generated induction fields able to be transmitted therethrough with virtually no diminution in strength. Thus, the actual cooking surface can be a continuous planar area. However, in that the generated induction field of each heating unit has a downwardly as well as upwardly directed component, the units could not be held in position against the glass surface by an arrangement which included materials disposed sub-adjacent the heating unit that would intercept the induction field and become heated therefrom, i.e., generally including any metals. Thus, heretofore as exemplified by the commercial embodiment of a cooking surface utilizing induction heating units and manufactured by the assignor of the present invention, the heating coils were sandwiched between the undersurface of the glass and a Transite sheet, such as disclosed in U.S. Pat. No. 3,796,850 having a common assignee, with the Transite sheet extending laterally beyond the fringes of the flux field to permit it to be engaged by a metal framework which then urged the Transite sheet towards the glass to maintain the coil in this position by a squeezing force. However, it was found that during shipment, the shock forces encountered by such an arrangement permitted the lateral displacement of the heating unit to the extent that upon reaching its destination the heating unit was not in alignment with the indicia on top of the cooking surface indicating the cooking area. This then required a service call to realign the heating unit with such indicia.
Further, the ceramic sheet was typically framed by a stainless steel trim piece and, in that it is important to prevent any spillage from leaking between the trim and the glass to the space below generally housing the electrical components, the trim was sealed to the glass by depositing therebetween a bead of self-curing silicone adhesive. This required certain special handling in the assembly of the trim to the glass and further required a certain time delay for the adhesive to become cured.
Also, although the glass cooking surface had sufficient strength, even though only partially supported over its lateral extent by the sub-adjacent framework, to withstand a standard safety test against breakage by objects being dropped thereon, with the electrical equipment being generally disposed in a space immediately below the cooking surface, it remained possible for an uncommon accident to break through the glass surface and thereby expose the electrical equipment.